It is known that an oil or fat containing diacylglycerol at a high concentration has physiological actions such as an action of inhibiting an increase in a postprandial blood triglyceride (neutral fat) level and a reduced bioaccumulation potential (see, for example, Patent Documents 1 and 2). On the other hand, there is a tendency that diacylglycerol easily crystallizes because diacylglycerol has higher melting point than triacylglycerol, and the precipitated crystals are hardly dissolved. Further, diacylglycerol is known to include 1,3-diacyl glycerol and 1,2-diacylglycerol which are generally in equilibrium at a ratio of 2:1.
A method of removing a high melting point portion in advance by wintering is known as a method of inhibiting the crystallization of an oil or fat. It is known that the content of a saturated fatty acid can be reduced by nearly 30 mass % by adding an emulsifier serving as a fractionation aid to an oil or fat containing diacylglycerol at a high concentration during wintering to achieve solid-liquid separation (Patent Document 3).
Further, oleic acid is considered to be a favorable fatty acid from the viewpoints of its taste and flavor and its heating stability (Patent Document 4) or the viewpoint of health benefits (Non Patent Document 1). Thus, an edible oil having a high content ratio of oleic acid has been demanded by consumers.